This invention relates to a device for the loading of air with a controllable amount of a powdery or fine granular material which is contained in a container by whirling or churning-up the material, the device also being capable of blowing the laden air out of the container. The device is particularly adaptable to load air with powdered magnesium oxide and to blow the loaded air out of a container into a heating device.
When operating an oil furnace, arrangements have heretofore been made to introduce into the burner and into the combustion gases a mixture of air and a material such as magnesium oxide in order to prevent in one respect noxious corrosion of exposed metal parts, and in another respect, to prevent soiling of the boiler, pipe conduits, fittings and exhaust gases.
However, with such arrangements, problems arise because the magnesium oxide powder is hygroscopic and causes clogging or plugging-up due to the presence of moisture. The clogging causes disturbances in the addition of magnesium oxide into the heating system, thereby causing operating difficulties in the whole combustion system. Devices are known which add the magnesium oxide by using stirring means or other machanical means and which add the magnesium oxide through a controllable aperture to an air stream which serves in the movement of the powder. These known devices have the disadvantages that the apertures plug up frequently, and continuous and constant blowing in of powder into the oil combustion arrangement is not assured. Also the powder may creep through packings into the mechanical means which might lead to operating problems. Devices for the whirling-up and blowing-out of powdery materials are also known where such an air stream is blown into an aperture of a container holding the material, such air stream being directed against the surface of the powder in order to whirl it up, and where the air stream exits together with the whirled-up material through another aperture.
These known devices do not produce whirling currents energetic enough to effect reliable dust production out of the powder storage so that the reservoir used with these devices may have a comparatively small capacity. Thus heating arrangements having several boilers must be furnished with several individual devices for each boiler, and large amounts of air are needed in order to raise the dust from the powdered material, a fact which necessitates large blower capacities. Furthermore no constant intensive raising of dust is obtained in that the loading of air with equally large amounts of powder is not accomplished when the surface of the powder in the reservoir sinks slowly, and it is difficult to raise the dust continually when it is all the way down at the bottom of the container and also to blow it out of the container.
Accordingly, an object of the present invention is to overcome the disadvantages of the known prior art devices by the provision of an arrangement for insuring a continuous, constant, and also controllable raising of dust or powdery material while having a large capacity for the powder, the device of the present invention making it possible to furnish large and even extremely large boiler arrangements with magnesium powder. The aforementioned object is attained, according to the present invention, by a device having an annular tube or conduit which is generally horizontally disposed in the upper free space of a container, the container being filled to the extent that some free space still remains at its top. The annular tube is disposed at a distance radially spaced from the cylindrical wall of the container. A plurality of nozzles are arranged on the annular tube, such nozzles being at least partially downwardly directed.
Essentially in the center of the cover of the container, there is arranged an essentially vertical double tube arrangement which is vertically and slidably mounted on the cover. The double tube arrangement carries the aforementioned annular tube. One tube of the double tube arrangement is connected at its lower end to the annular tube and is connected at its upper end to a conduit which supplies compressed air. The other tube of the double tube arrangement passes into the interior of the container with its lower end disposed substantially at or just above the height of the annular tube, thus forming the blow-out conduit for the air laden with the whirled or churned-up granular or powder material. This arrangement produces a strong whirling stream directed down towards the surface of the material as well as a whirling stream rotating in the direction of the circumference of the container. The air stream acts like a tornado or cyclone causing a dusting-up of the powder, and eventually breaks lumps and large particles by whirling and by knocking them against the wall of the container.
The amount of air required for blowing the dust upwardly and for blowing it out may be small, so that the energy requirement for providing the compression of air may be kept small. It is mainly possible for the blow-head, formed by the annular tube and its nozzles, to follow at a constant distance the slowly subsiding surface of the powdered material, so that constant raising of dust and loading of the air is obtained until the container is completely emptied. Thus it is possible to work with constant air pressure so that devices for changing the pressure of the air in correlation to the slow emptying of the container are not required. It is easy to proportion the amount of the powder which should be blown out, and how much of it should be contained in the air. At a certain constant air pressure the whirled or churned-up amount of powder is larger the closer the blow head is guided towards the surface of the bulk powder in the container. Thus the amount of powder blown out is regulated and kept constant by the speed at which the double tube arrangement, the annular tube, and its nozzles are guided downwardly. For this purpose, preferably the double tube arrangement may be coupled with a mechanical drive which effects a continual downward motion of the double tube arrangement, the speed of such motion being regulated by adjustment of the driving means.
Other features which are considered characteristic of the invention are set forth in the appended claims.
Although the invention is illustrated and described in relationship to specific embodiments, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claim.
The construction and operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.